I have some experience about Android phones (but i'm not an expert) .

I have problems with my Samsung Galaxy S2 (GT-I9100) . Its battery heating too much, there are a lots of applications, sometimes phone freezing and not responsing, it's battery consumption is too much and it's a little slow. And **sometimes restarting itself.**

In shortly, i'm using it for long time, i installed too many apps and uninstall some of them. Now i want to clear everything (except SD card datas) , delete all datas / apps . And start from origin, again. I'll my (really needed) applications from Google Play, later.

In computer knowledge, it's mean *format* , i think.

But for mobile phones, I'm not sure, it's called as "formatting" or "firmware reinstalling" . 

I plugged my phone to computer and launch Samsung Kies but there isn't *reinstall firmware* option. 

**Notes**

1. Android version : 4.0.3

1. My phone isn't rooted. (and i won't do that)

1. I'm worring about warranty. So, please just *legal* methods.

1. I don't want to lose my datas (music, etc) on my SD CARD.

1. I don't want to send my phone to technical service for this. It'll take at least 4-5 days.